1. Field of the Invention
The invention concerns a disposable diaper, specifically one having a target strip for a pair of adhesive closure tabs. In particular, the invention concerns the manufacture of the target strip.
2. Description of the Related Art
Disposable diapers typically have an outer shell of thin plastic film such as polyethylene, which is reinforced at the areas where adhesive closure tabs are adhered during fastening of the diaper around a wearer. The reinforcement frequently is a stronger plastic film that is adhesively attached to the outer shell and is often called a "target strip". A typical method of continuously making and applying the target strip includes the steps of: a) unwinding a roll of pressure-sensitive adhesive tape having a backing such as biaxially oriented polypropylene ("BOPP") film that has a low-adhesion backsize coating on its nonadhesive face, b) cutting the tape into pieces, and c) adhering one piece of the tape by its pressure-sensitive adhesive layer to the outer shell of each diaper to provide a target strip. While the low-adhesion backsize coating permits the tape to be unwound from the roll, it has a deleterious effect on adhesion of the adhesive closure tabs to the target strip. Although this problem can be avoided by employing a release liner instead of a low-adhesion backsize coating, doing so would be more expensive.
The problem of poor adhesion of the closure tabs to a low-adhesion backsize coating can also be avoided by coating the adhesive onto the backing film of the target strip on-line with the diaper-making operation. However, at the high speeds used in diaper-making lines, this results in an adhesive coating that may be undesirably uneven in thickness and may deviate excessively from the edges of the film.
3. Other Prior Art
U.S. Pat. No. 3,165,992 (Jeffries) concerns film adhesives that may or may not be normally tacky and typically are wound up with a double-coated release paper. Jeffries concerns the problem that after the adhesive film has been unwound and applied to an object, the release paper can be difficult to remove. Jeffries solves this problem by abrading away at least part of the release coating at one face of the release paper, thus permitting easy removal of the release paper by applying a pressure-sensitive adhesive tape to the abraded surface.
U.S. Pat. No. 3,271,229 (Grabovez) physically abrades the surface of a thermoplastic film such as poly(ethylene terephthalate) or polypropylene to provide improved slip, i.e., lower friction; the abrasion is accomplished with a brush having non-metallic bristles or fibers. U.S. Pat. No. 2,951,305 (Seymour) physically abrades poly(ethylene terephthalate) film with a wire brush in order to dull its surface appearance. Neither Grabovez or Seymour suggests that the surface being abraded might have first received any sort of coating.